In the conventional hot-rolling method, only roll-cooling water is used for protecting a roll, but now a rolling oil is used for reducing the rolling load and decreasing wear of the roll, and an excellent effect is attained thereby.
The main object of the conventional lubricant for hot rolling is to reduce wear of a work roll and improve the roll surface, because the requirement for the quality of a rolled product is relatively moderate and the thermal crown of the work roll is not regarded as important. Nevertheless, recently, an increased quality of the product has been demanded, and the effect of reducing the thermal crown of the work roll, which has a direct adverse influence on the quality of the product, has become important.